Be respectful when using social media
After all is said and done, don't go and ruin your conscientious cast-off with sloppy social media gaffes. Writing about your relationship on the Internet is the verbal equivalent of standing on a tall platform in front of all of your mutual friends loudly shouting, "Sarah didn't cut it. I'm on the market again! Bring out the Champagne!"
A few rules of thumb regarding social media:
1. The high road is paved with silence. This means not tweeting, blogging or status-updating about the details of your relationship's demise, even cryptically. (See: Chris Brown, Ashton Kutcher, etc.) This also means refraining from discussing new love interests/one night stands online for a courtesy period of roughly 2-5 months. Talk to your friends about this stuff over a beer, like you did before the Internet existed.
2. Follow her lead when it comes to changing your relationship status. If she changes it to single, feel free to follow suit. If she doesn't, remove the relationship status entirely and delete the post denoting the change off your timeline. She doesn't need to see dozens of your friends commenting on it, whether it's with enthusiasm or sadness.
3. Discuss de-friending one another to avoid painful complications like the ones described above. I say discuss, because that's better than just doing it, especially if you worked in the "let's stay friends" line (because you know you did). Ultimately, this is the fastest way to healing (for her) and moving on (for you).
Good luck dropping the bomb. Hopefully the whole relationship-deactivation thing goes smoothly. And remember, when in doubt, don't blog about it.